What stands between the source and a temperature estimate?
Detector response varies with wavelength. Calibration connects recorded signals to physical radiance or flux, while spectral coverage determines which part of the source distribution is available for comparison.
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EXPLORE THE MODEL
The thermal shape of light
Bλ = (2hc²/λ⁵) / [exp(hc/λkT) − 1]
Each curve is divided by its own sampled peak. This view compares shape; brightness cannot be compared.
Read sampled numerical values
| Vacuum wavelength (nm) | 6000 K | 3000 K reference |
|---|---|---|
| 100 | 1.441e-5 | 1.777e-14 |
| 390 | 0.888 | 0.061 |
| 680 | 0.78 | 0.713 |
| 970 | 0.402 | 1 |
| 1,260 | 0.206 | 0.857 |
| 1,550 | 0.113 | 0.635 |
| 1,840 | 0.066 | 0.452 |
| 2,130 | 0.041 | 0.321 |
| 2,420 | 0.027 | 0.231 |
| 2,710 | 0.018 | 0.168 |
| 3,000 | 0.013 | 0.125 |
Use the normalized view to compare shape and the fixed radiance scale to compare brightness. Hotter ideal emitters peak at shorter wavelengths and emit more at every wavelength. A thermal shape alone cannot establish elemental composition.
What this model can establish
Blackbody spectral radiance per unit vacuum wavelength. An ideal continuum is not a measured stellar spectrum; atmospheres, dust, spectral lines and instrument response are omitted. The peak depends on the spectral convention.
Optional: check your understanding
MAKE THE CONNECTION
A detector suppresses blue light more strongly than red light. What is needed before fitting a source temperature?
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HISTORY THROUGH EVIDENCE
A curve that had to face data
Planck’s 1900 treatment made thermal-radiation spectra central to the emergence of quantum theory.
Explore how the evidence changed the explanation →